1. Field of the Invention
The present invention generally relates to a compression-expansion power device or mechanism preferably, but not necessarily, in the form of a cylinder with opposed pistons mounted therein and connected to opposed crankshafts for reciprocation of the pistons in relation to each other and in relation to the cylinder for compressing and expanding gases in accordance with the "Zachery" cycle with the device being arranged for generating the maximum torque possible from the gas pressure available and yielding a substantial increase in thermal efficiency as compared to other variable volume devices.
2. Description of the Prior Art
The thrust of new designs in energy conversion devices has generally centered on means of increasing thermal efficiency and thereby decrease fuel consumption for a given work ouput. Improvements in thermal efficiency of internal combustion engines operating on the Otto cycle or Diesel cycle have in the past been largely directed at improving the preignition and burning characteristics of fuels since it has long been known that increasing the compression ratio of such engines will increase their thermal efficiency. Engines that require super-charging by virtue of their design such as two cycle engines and U.S. Pat. No. 2,486,185 cited below, wherein exhaust gases are expelled through exhaust ports by inlet air under pressure, have directed their improvements at decreasing fuel losses through the exhaust ports during the scavenging process and the thermal efficiency losses inherent in supercharging are accepted as part of the nature of the design. Supercharging of spark ignition engines has virtually been abandoned, except for special applications where fuel economy is not of prime importance, because of the drastic reduction in thermal efficiency resulting from the decrease in compression ratio required in order to avoid preignition of the fuel. Improvements in overall thermal efficiency of internal combustion engines have also been made by using exhaust turbines to further expand exhaust gases prior to release to the atmosphere.
Power devices in the form of opposed piston engines using the Otto cycle and Diesel cycle have been known for many years and some embodiments of these engines have been in use. Such devices normally employ opposed pistons which reciprocate at the same frequency with ignition of the combustible mixture occuring near the point of highest pressure and lowest volume between the pistons which occurs when the two pistons simultaneously reach their innermost point of cyclic movement or near top dead center. Such devices theoretically afford no increase in thermal efficiency as compared to non-opposed similar engines.
In addition to this type engine, the following list of patents is exemplary of developments which have occurred in this type of structure in which one piston travels at a different rate of speed than the other and the pistons are out-of-phase so that the overlapping portions of the path of movement of the pistons will occur at different intervals of the cycle of movement of each piston.
______________________________________ 670,966 Apr. 2, 1901 1,168,877 Jan. 18, 1916 1,237,696 Aug. 21, 1917 1,689,419 Oct. 30, 1928 2,160,687 May 30, 1939 2,345,056 Mar. 28, 1944 2,473,759 June 21, 1949 2,486,185 Oct. 25, 1949 3,485,221 Dec. 23, 1969 ______________________________________
It appears that of the above patents none are exemplary of the necessary arrangements of their commonly known parts that will theoretically or practicably achieve a significant increase in thermal efficiency over that obtainable from a standard Otto cycle or Diesel cycle engine.
Of the above listed patents, Mallory, U.S. Pat. No. 2,486,185 discloses an engine having a cylinder with opposed pistons mounted therein and connected to crankshafts at each end of the cylinder with one of the crankshafts being connected to the other so that the two crankshafts have a turning ratio of 2:1 with the angular orientation of the crankshafts and, the pistons attached thereto, being such that when the slow speed piston is at its inner dead center, the fast speed piston is approximately 90.degree. advanced past its outer dead center position, which arrangement accomplishes the purpose of controlling an exhaust port by the slow speed piston. The cylinder includes an exhaust port that begins to become uncovered by the slow speed piston when it has moved approximately 125.degree. from inner dead center. The cylinder is also provided with a centrally located port and chamber with air and fuel admission to the chamber controlled by valves such that an air charge is admitted to the cylinder starting at approximately the time of first uncovering of the exhaust port and continuing until the slow speed piston has almost recovered the exhaust port at which time the fuel valve is opened and air and fuel intake continue until the largest intake volume is achieved at which time the air and fuel valves are closed and the compression stroke begins. This arrangement allows for the complete exhaust of the burnt gases before fuel is introduced providing sufficient supercharging is used. Mallory states that inlet air under pressure is essential for operation in the stroke configuration of FIG. 8 of U.S. Pat. No. 2,486,185. It is evident that this configuration will not operate without supercharging since the volume decreases after the slow speed piston closes the exhaust port and no fresh air can be taken in leaving the chamber and cylinder volume completely filled with burnt gases at the beginning of the compression stroke. As a result of the arrangement of the intake port, the piston controlled exhaust port and the phase relationship between the pistons and the crankshafts, the storke ratio configurations of FIGS. 7 and 9 of U.S. Pat. Nos. 2,486,185 leave residual burnt gas volumes of about 65% and 35% respectively of the total possible intake volume remaining when the exhaust port is closed by the slow speed piston and it is probable that the Mallory engine in these stroke ratio configurations would also have to be supercharged in order to be operative. In U.S. Pat. No. 2,486,185 the midpoint displacement of both pistons occurs at 90.degree. and 270.degree. and the midpoint displacement of the fast speed piston also occurs at 0.degree. and 180.degree. which phase relationship results in the overlap or commonly used space in the cylinder being very minimal; approximately 5% of the stoke for the configuration of FIG. 7, approximately 3% of the stroke for FIG. 8 and less than 0% or no commonly used space for FIG. 9 if a clearance of 25 one hundredths inches is retained at the point of closest approach. Moreover, in U.S. Pat. No. 2,486,185 the maximum lever arm of the slow speed crankshaft occurs approximately 42.degree. beyond the point of least volume at which point the gas has expanded to approximately 50% of the final expansion volume and the pressure is greatly reduced.